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81.
The public perception of climate change is characterized by heterogeneity, even polarization. Deliberative discussion is regarded by some as key to overcoming polarization and engaging various publics with the complex issue of climate change. In this context, online engagement with news stories is seen as a space for a new “deliberative democratic potential” to emerge. This article examines aspects of deliberation in user comment threads in response to articles on climate change taken from the Guardian. “Deliberation” is understood through the concepts “reciprocity”, “topicality”, and “argumentation”. We demonstrate how corpus analysis can be used to examine the ways in which online debates around climate change may create or deny opportunities for multiple voices and deliberation. Results show that whilst some aspects of online discourse discourage alternative viewpoints and demonstrate “incivility”, user comments also show potential for engaging in dialog, and for high levels of interaction.  相似文献   
82.
Hypoxic blackwater events occur when large amounts of organic material are leached into a water body (e.g., during floodplain inundation) and rapid metabolism of this carbon depletes oxygen from the water column, often with catastrophic effects on the aquatic environment. River regulation may have increased the frequency and severity of hypoxic blackwater events in lowland river systems, necessitating management intervention to mitigate the impacts of these events on aquatic biota. We examine the effectiveness of a range of mitigation interventions that have been used during large-scale hypoxic blackwater events in the Murray–Darling Basin, Australia and that may be applicable in other environments at risk from hypoxic blackwater. Strategies for hypoxia mitigation include: delivery of dilution flows; enhancement of physical re-aeration rates by increasing surface turbulence; and diversion of blackwater into shallow off-channel storages. We show that the impact of dilution water delivery is determined by relative volumes and water quality and can be predicted using simple models. At the dilution water inflow point, localized oxygenated plumes may also act as refuges. Physical re-aeration strategies generally result in only a small increase in dissolved oxygen but may be beneficial for local refuge protection. Dilution and natural re-aeration processes in large, shallow lake systems can be sufficient to compensate for hypoxic inflows and water processed in off-channel lakes may be able to be returned to the river channel as dilution flows. We provide a set of predictive models (as electronic supplementary material) for estimation of the re-aeration potential of intervention activities and a framework to guide the adaptive management of future hypoxic blackwater events.  相似文献   
83.
Natural gas often contains high concentrations of hydrogen sulfide which must be removed before the gas can be transmitted by pipeline. Sour gas plants extract the sulfur, by converting it to elemental sulfur through a modified Claus process. The sulfur recovery is 93% for small plants (10–100 tonnes of sulfur per day) to 99% for large plants (1000–4000 tonnes of sulfur per day). The unrecovered sulfur is Incinerated giving rise to relatively small emissions of SO2 characterized by high buoyancy and low momentum.

Using a unique aerial probing methodology, plume dispersion studies were conducted on two plants located fn the foothills of southwestern Alberta, Canada. These studies were generally conducted under neutral conditions and with westerly air flows typical of Chinook conditions. Notable variations of the plume dispersion parameters from accepted predictive values were found, indicating that such values cannot be used with confidence to estimate plume rise and dispersion in the mountain foothills.  相似文献   
84.
In studies of commercial fishing, little attention has been paid to the use of bait. We examined lobster fishery bait-to-catch ratios in St. Margaret's Bay and Mahone Bay, Nova Scotia. Data were obtained from the Fishermen and Scientists Research Society's Lobster Recruitment Project. Local ecological knowledge of the resource users from within the study area was also gathered using semi-structured interviews. The estimated amount of bait required to catch each lobster, weighing about 480 g, ranged from 185 g (November) to 1455 g (April) for average months during the 2002/3, 2003/4 and 2004/5 fishing seasons. We estimated the overall ratio of bait-to-catch to be about 1.9 units of bait per unit of catch. The eco-efficiency and food-supply implications of consuming more bait than product in a fishery are outlined.  相似文献   
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Three methods for predicting element mobility in soils have been applied to an iron-rich soil, contaminated with arsenic, cadmium and zinc. Soils were collected from 0 to 30 cm, 30 to 70 cm and 70 to 100 cm depths in the field and soil pore water was collected at different depths from an adjacent 100 cm deep trench. Sequential extraction and a column leaching test in the laboratory were compared to element concentrations in pore water sampled directly from the field. Arsenic showed low extractability, low leachability and occurred at low concentrations in pore water samples. Cadmium and zinc were more labile and present in higher concentrations in pore water, increasing with soil depth. Pore water sampling gave the best indication of short term element mobility when field conditions were taken into account, but further extraction and leaching procedures produced a fuller picture of element dynamics, revealing highly labile Cd deep in the soil profile.  相似文献   
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89.
Spatial variability of ammonium and nitrate in soils near a poultry farm   总被引:1,自引:0,他引:1  
This paper assesses the distribution of ammonium (NH4+) and nitrate (NO3-) nitrogen deposition in native bushland soil adjacent to an open ventilated poultry farm. The farm is located in Thirlmere 150 km south west of Sydney, Australia. A total of 104 geographically referenced soil cores were obtained from the study area. Soil pH, electrical conductivity (EC), NH4(+) - and NO3(-)-nitrogen concentrations were analysed for variable trends at three depths, i.e. 0-30, 30-60, and 60-90 cm. Significantly higher concentrations of the two nitrogen forms and EC were observed nearer to the farm in the surface soil samples (0-30 cm). The distribution of NH4+, NO3- and EC were all correlated in surface samples throughout the study area. There was no indication of NH4+ and NO3- leaching within soil profile sampled and it appears that weeds and native vegetation had utilised the accumulated nitrogen. The level of N deposition adjacent to the poultry farm decreased downwind due to dispersion of plume and to the buffering effects from the bushland.  相似文献   
90.
Although petroleum contamination has been identified at many Antarctic research stations, and is recognized as posing a significant threat to the Antarctic environment, full-scale in situ remediation has not yet been used in Antarctica. This is partly because it has been assumed that temperatures are too low for effective biodegradation. To test this, the effects of temperature on the hydrocarbon mineralisation rate in Antarctic terrestrial sediments were quantified. 14C-labelled octadecane was added to nutrient amended microcosms that were incubated over a range of temperatures between -2 and 42 degrees C. We found a positive correlation between temperature and mineralisation rate, with the fastest rates occurring in samples incubated at the highest temperatures. At temperatures below or near the freezing point of water there was a virtual absence of mineralisation. High temperatures (37 and 42 degrees C) and the temperatures just above the freezing point of water (4 degrees C) showed an initial mineralisation lag period, then a sharp increase in the mineralisation rate before a protracted plateau phase. Mineralisation at temperatures between 10 and 28 degrees C had no initial lag phase. The high rate of mineralisation at 37 and 42 degrees C was surprising, as most continental Antarctic microorganisms described thus far have an optimal temperature for growth of between 20 and 30 degrees C and a maximal growth temperature <37 degrees C. The main implications for bioremediation in Antarctica from this study are that a high-temperature treatment would yield the most rapid biodegradation of the contaminant. However, in situ biodegradation using nutrients and other amendments is still possible at soil temperatures that occur naturally in summer at the Antarctic site we studies (Casey Station 66 degrees 17(') S, 110 degrees 32(') E), although treatment times could be excessively long.  相似文献   
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